Coffee Cherry Structure: Understanding the Silver Skin of Coffee Beans and Its Impact

For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat official account: cafe_style)

FrontStreet Coffee - Introduction to Coffee Bean Structure

The essence of coffee beans is plant seeds. After coffee cherries (commonly known as coffee fruits) are harvested when ripe, they must undergo a series of processing steps to transform from seed to cup. Let's explore the internal structure of coffee cherries to better understand and appreciate coffee! As shown in Figure 1, parts 1 through 7 are respectively: center line, seed, silver skin, inner pericarp, pectin layer (pulp), mesocarp, and outer skin.

1: Center cut - Center line

2: Bean (endosperm) - Coffee bean

3: Silver skin (testa, epidermis) - Silver skin

4: Parchment (hull, endocarp) - Parchment layer

5: Pectin layer - Pectin layer

6: Pulp (mesocarp) - Fruit pulp

7: Outer skin (pericarp, exocarp) - Outer pericarp

Sometimes you might notice some yellowish-brown flakes in roasted coffee beans or coffee powder - this is "silver skin." Silver skin is a thin membrane attached to green coffee beans. The silver skin in the middle crease of coffee beans is called inner silver skin, while that on the outside is called outer silver skin. During the roasting process, most of the coffee silver skin gradually falls off and is expelled, while the inner silver skin is generally difficult to remove.

The small amount of outer silver skin that isn't expelled gets scorched by the high temperature in the roasting drum, resulting in a slight astringency after extraction, which somewhat affects the purity of the taste but adds more complexity to the flavor profile.

Inner silver skin rarely falls off and is expelled. Since it undergoes green bean processing along with the coffee beans, it carries some origin-specific flavor attributes. After roasting, the inner silver skin provides a pleasant astringency and makes the coffee's flavor layers more complex.

Although silver skin affects the flavor and mouthfeel of coffee, it also enhances the complexity and richness of the coffee. If the silver skin were completely removed, the coffee's taste would inevitably become somewhat monotonous.

Key Knowledge Point

When using the same water, time is the key factor for adjusting the amount and variety of extracted substances.

In summary: FrontStreet Coffee is a coffee research house dedicated to sharing coffee knowledge with everyone. We share everything without reservation, hoping to help more friends fall in love with coffee. Every month, we hold three coffee tasting events with significant discounts. The reason is that FrontStreet Coffee wants to let more friends enjoy the best coffee at the lowest possible price - this has been our mission for the past six years!

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473